I just migrated my Ubuntu iSCSI storage server to Ubuntu 12.04 which ships with a new iSCSI implementation: LIO (linux-iscsi.org). Aside from the fact that this project lacks a HUGE amount of documentation I want to share this problem with you:
kernel: Exiting Time2Retain handler because session_reinstatement=1
This happens if you access LUNs from more multiple nodes (as required for RAC setups) while all nodes share the same initiatorname.
The fix is to use different and unique initiatornames for every node.